1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
|
--- a/plugins/ipc/ipc.hpp
+++ b/plugins/ipc/ipc.hpp
@@ -33,6 +33,18 @@
/** Handle incoming data on the socket */
std::function<void(uint32_t)> handle_fd_activity;
void handle_fd_incoming(uint32_t);
+
+ /** Outgoing bytes not yet written because the reader is slow/backpressured. */
+ std::vector<char> out_buffer;
+ size_t out_sent = 0;
+ bool want_writable = false;
+
+ /** Append bytes to the outgoing queue. */
+ void queue_output(const char *data, size_t size);
+ /** Try to drain the outgoing queue; arms a writable watch on EAGAIN. */
+ void flush_output();
+ /** Toggle WL_EVENT_WRITABLE interest on the client's event source. */
+ void set_writable_watch(bool on);
};
/**
--- a/plugins/ipc/ipc.cpp
+++ b/plugins/ipc/ipc.cpp
@@ -10,6 +10,7 @@
#include <sys/ioctl.h>
#include <unistd.h>
#include <cstring>
+#include <cerrno>
/**
* Handle WL_EVENT_READABLE on the socket.
@@ -147,6 +148,7 @@
static constexpr int MAX_MESSAGE_LEN = (1 << 20);
static constexpr int HEADER_LEN = 4;
+static constexpr size_t MAX_OUTPUT_QUEUE = 16u * 1024 * 1024;
wf::ipc::client_t::client_t(server_t *ipc, int fd)
{
@@ -205,6 +207,11 @@
return;
}
+ if (event_mask & WL_EVENT_WRITABLE)
+ {
+ flush_output();
+ }
+
int available = 0;
if (ioctl(this->fd, FIONREAD, &available) != 0)
{
@@ -291,47 +298,95 @@
close(this->fd);
}
-static bool write_exact(int fd, const char *buf, ssize_t n)
+void wf::ipc::client_t::queue_output(const char *data, size_t size)
+{
+ out_buffer.insert(out_buffer.end(), data, data + size);
+}
+
+void wf::ipc::client_t::set_writable_watch(bool on)
+{
+ if (on == want_writable)
+ {
+ return;
+ }
+
+ want_writable = on;
+ wl_event_source_fd_update(source,
+ WL_EVENT_READABLE | (on ? WL_EVENT_WRITABLE : 0));
+}
+
+void wf::ipc::client_t::flush_output()
{
- while (n > 0)
+ while (out_sent < out_buffer.size())
{
- ssize_t w = write(fd, buf, n);
- if (w <= 0)
+ ssize_t w = write(fd, out_buffer.data() + out_sent, out_buffer.size() - out_sent);
+ if (w > 0)
{
- return false;
+ out_sent += (size_t)w;
+ continue;
+ }
+
+ if ((w < 0) && (errno == EINTR))
+ {
+ continue;
}
- n -= w;
- buf += w;
+ if ((w < 0) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
+ {
+ // Reader is slow: keep the remainder queued and flush when writable
+ // instead of dropping the connection on transient backpressure.
+ set_writable_watch(true);
+ return;
+ }
+
+ LOGE("Error sending json to client!");
+ shutdown(fd, SHUT_RDWR);
+ out_buffer.clear();
+ out_sent = 0;
+ set_writable_watch(false);
+ return;
}
- return true;
+ out_buffer.clear();
+ out_sent = 0;
+ set_writable_watch(false);
}
bool wf::ipc::client_t::send_json(wf::json_t json)
{
- bool status = false;
+ bool status = true;
json.map_serialized([&] (const char *buffer, size_t size)
{
if (size > MAX_MESSAGE_LEN)
{
LOGE("Error sending json to client: message too long!");
- shutdown(fd, SHUT_RDWR);
+ status = false;
return;
}
uint32_t len = size;
- if (!write_exact(fd, (char*)&len, 4) || !write_exact(fd, buffer, len))
- {
- LOGE("Error sending json to client!");
- shutdown(fd, SHUT_RDWR);
- return;
- }
-
- status = true;
+ queue_output((const char*)&len, sizeof(len));
+ queue_output(buffer, size);
});
- return status;
+ if (!status)
+ {
+ shutdown(fd, SHUT_RDWR);
+ return false;
+ }
+
+ if ((out_buffer.size() - out_sent) > MAX_OUTPUT_QUEUE)
+ {
+ LOGE("IPC client output backlog too large; dropping connection");
+ shutdown(fd, SHUT_RDWR);
+ out_buffer.clear();
+ out_sent = 0;
+ set_writable_watch(false);
+ return false;
+ }
+
+ flush_output();
+ return true;
}
namespace wf
|
